


Belonging to Secrets

by pinkpines



Category: Gravity Falls
Genre: Aged-Up Character(s), F/M, Fluff and Angst, Kissing in the Rain, Outdoor Sex, Rain Sex, Sibling Incest, pinecest - Freeform
Language: English
Status: Completed
Published: 2015-11-23
Updated: 2015-11-23
Packaged: 2018-05-03 00:30:58
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,137
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5269778
Author URL: https://archiveofourown.org/users/pinkpines/pseuds/pinkpines
Summary: <blockquote class="userstuff">
              <p>After a particularly difficult phone conversation with her mother, Mabel runs outside in the middle of a storm. Dipper chases after her and attempts to comfort her.</p>
            </blockquote>





	Belonging to Secrets

**Author's Note:**

> Written after I was given the prompt "Kiss in the Rain" by an anonymous on tumblr. It turned into... whatever this smutty thing is.
> 
> You can find the original post here: http://pinkpines.tumblr.com/post/133166445671/i-want-the-k
> 
> Pinecest is inevitable here. If it's your thing, hey there, it happens to be my thing too. Have a seat, I hope you enjoy it.

It was the sort of storm that you didn’t want to be in, and yet, there Dipper was, chasing Mabel through the street, calling after her. He couldn’t be sure if she was actually unable to hear him shouting for her to slow down or if it was a case of Mabel being so upset she was pretending not to hear anything he was saying.

He found himself turning a corner from their apartment, the street was emptier than he could ever remember seeing it. And there was Mabel, storming ahead, unyielding, even in this weather.

“Mabel, would you stop already?” He shouted, out of breath from being so woefully out of shape. He was squishy in the worst sense. He definitely couldn’t keep this up forever. He managed to catch up to her enough that with his last burst of energy he stopped just in front of her, holding his arms out as though to prevent her from passing him.

It was only then that Dipper got a good solid look at Mabel’s face. She was soaked to the bone, but then again so was he. In the darkness it would have normally been hard to make out her features but of course, Dipper had hers memorized. Though the rain had her hair completely saturated and streaming rivulets down her face, he just  _knew_  she was crying. The realization made him falter for a moment.

After all, he knew she was upset, but he had no idea it was bad enough that it had actually made her _cry_.

“Hey. Stop running and  _talk_  to me.”

“It’s just…” Mabel sniffled and leaned against the side of the building they were standing in front of. It was an old tenement building. It was a quarter past midnight and he doubted anyone was awake but if they were? They probably thought Dipper and Mabel were out of their minds for being caught in the middle of this torrential downpour. Dipper would be inclined to agree with that, in all honesty.

His wet hair kept slipping into his face, obscuring his field of vision. Pushing his hand over his forehead and through his hair he gave her a steady look, almost willing her to finish.

“It’s just what?”

“It’s just…  _so hard_. All the time. It’s  _always_  something. Why can’t it ever just be easy for us to be together?”

And just like that, Dipper’s heart lurched in his chest. Her bloodshot eyes were telling enough, but to hear her earnest words was another thing entirely.

Mabel was right. Ever since they had decided to be together it hadn’t been easy. The moment Dipper and Mabel decided to be in a relationship meant everything had to be different. It had to be secret and hidden. It had to include lies to the people who cared about them and loved them. It meant that they both had to go on the occasional failed blind date that their family or friends set them up on.

It meant they could never just simply be together. Not the way other people could be.

Truthfully it was frustrating, and impossible to handle. But for Dipper, dealing with those things meant that he could stay with Mabel and really, that was all he fucking cared about.

“I’m sorry,” he sighed, reaching out and touching the side of her face. Her gaze softened a bit and Dipper continued. “You’re right. It’s hard. You don’t deserve this, Mabel. You deserve a lot more than I can give you, if I’m being honest with myself.” He frowned, his thumb tracing over her cheek. “You deserve someone who can do the whole grand-gesture thing. Someone who can shout it from the rooftops. And, I don’t think I can ever give that to you.”

“Dipper…” She launched herself towards him and wrapped her arms around him tightly. They were both soaking wet, clothes stuck to their bodies, and cold rain pooling in their shoes as he took a few steps back to accommodate the added weight of Mabel in his arms.

“Listen, I’m sorry about tonight. About all of it.” He wrapped his arms around her firmly, holding her close against his chest. Their parents had decided that tonight was the night to be critical of Mabel’s lovelife- or lack thereof. Their mother even thought it fitting to mention that Mabel  _really_  ought to consider moving out of their shared apartment if she wanted to find a nice boy to settle down with.

The entire thing had been the catalyst for this moment. Sure, their mother meant well, but that was hardly a consolation to Mabel, who took the criticism to heart.

“I don’t care what anyone else has to say about either of us. I…I know this is where I’m supposed to be.” His hand smoothed over her wet shirt, rubbing against her back in rhythmic circles.

“I belong with you, Mabel. I don’t care what anyone thinks, or how hard it is. We’re supposed to be together. I don’t care if no one ever understands that… just as long as you feel the same way, too. That’s all that matters to me.”

Before he could even come up with another comforting thing to say, Mabel’s arms were around his neck, pulling him firmly towards her, lips pressed against his as they stumbled backwards and into the poorly lit alleyway along the side of the building.

She’d managed to back Dipper up so that he was pressed against the brick exterior of the building, her fingernails lightly scratching along his scalp in a way that made him hum against her lips.

Apparently he had done a good job at getting his point across to her.

“I love you, Dipper,” she sighed wistfully, a resignation against his mouth. It was almost like she was declaring it but also surrendering to it all at once. Her voice was quiet and small, a rarity for Mabel, really.  “I’m just so freaking tired of thinking and worrying about everyone else. For once it would be nice to only have to worry about each other.”

With that, Mabel leaned against him, chest to chest, her body weight shifting so that Dipper was supporting her weight as he leaned between her and the brick wall behind him. He was pinned in the dark, a lone streetlight providing the only light that shined off of Mabel’s long wet hair.

The rain had caused their clothes to completely saturate, and as she leaned against him with her face pressed against his neck, Dipper could feel the curves and lines of her body through their wet shirts. In the cold night, they were generating a small amount of heat between her heart and his. Dipper could feel the warmth spread from his chest, moving outward slowly to the rest of him.

“So, don’t worry about them anymore.”

It may have been dark but Dipper knew Mabel’s body well enough to know that underneath the shirt she was wearing (his shirt, actually) she wasn’t wearing much, if anything underneath it. He couldn’t help that his hands were dying to explore the expanses beneath it. Dipper’s grabbed her hips and held hers flush against his as he moved his mouth to bite teasingly at her lips before kissing her once more.

“Let me worry about everything.”

Spinning them easily, he reversed their positions so that Mabel was now standing with her back against the building as Dipper’s hands slid up underneath the well-worn but flimsy t-shirt she had on, which had  _PIEDMONT MATHLETES_ in large block lettersstretched across her chest.

The rain had cooled her skin but his hands were perpetually warm, and snaked up her stomach, past her ribs. Soon he was pressing his palm against  the curve of her breast, kneading it slowly with his hand as his thumb grazed the taut peak hidden from his view.

“ _Ah_ , Dipper,” Mabel sighed and arched her back so that she was pressing against his hand with need. For a moment he thought she might protest such an overtly public display of affection. They had never dared to be this bold, actually. Instead Dipper was utterly pleased to find that in response, Mabel had already hooked a leg around his hips, her other foot on tiptoe to better reach his mouth with hers. The front of her hips pressed against the front of his jeans enough that it made him groan against her lips.

Quickly he used his free hand to reach down behind Mabel, grasping the back of her thigh and hoisting her enough that she hooked both of her legs around him and leaned back against the brick wall to help support her weight as he began to push her shirt up over her stomach.

Dipper was admiring the sight of her pale smooth stomach and cute little belly button in this interesting lighting when she hesitated for a moment. It was subtle but he caught it, because it was her, and he and Mabel hadn’t needed to express themselves solely with words since they were six.

The shirt stopped just below the swell of her breasts and a large hand reached out to grasp her daintier one, easily threading their fingers together and squeezing them gently.

“Hey, I’ve got you.” His nose, red from the cold, nudged against hers. He could feel her relax a bit.

“No one can see us here,” his breath was ghosting against her lips as he be lifted their joined hands to rest against the wall beside Mabel’s head. His birthmark pressed against her forehead and they smiled at each other. “It’s just me and you.”

And just like that he was lost in her. In her taste, her touch, the way her tongue rolled against his to a rhythm that was all their own. It was the sort of harmony you had to be a part of to really hear.

But they could hear it as loud as the rain hitting against the pavement.

Clumsy was the best way to describe his movement as he tugged her shirt up to her clavicle, craning his head down to pull one of her rosy peaks into his mouth. When she gasped it only spurred him on, and he sucked a little harder, teeth grazing against the nub in his mouth until Mabel started to squirm and moan. His mouth tore itself from her perky breasts, petite but perfect in the way they fit in his hands, and into his mouth, and he kissed her again because it came as easily as breathing.

He thrust his hips a bit against her, feeling his denim-clad erection press against the soft flesh between her thighs. Mabel couldn’t see what was pressed against her, her skirt was obscuring the view slightly, but from the way she squirmed in response, he knew she could feel it.

Untangling their linked fingers he focused on getting both hands underneath her skirt, reaching down to rub his fingers against her through the fabric of her panties.

“You’re soaked,” he flashed a lopsided grin her way and Mabel blushed but giggled anyway, a good double entendre not ever lost on her.

“You’re  _so_  dumb,” she spoke quietly, her breath hitching when he pushed her panties to the side and slid his fingers against her slick folds.

“The  _dumbest_ ,” he nodded, sucking at her neck as he slid a teasing finger to circle over her entrance slowly, and trail back to her clit, rubbing slow purposeful circles against it until her hips were undulating and rolling against him invitingly.

Mabel had a lot of little tells that let Dipper know how she was feeling, if she liked something, if she was close to cumming, that sort of thing. When he looked up at her face, drops of water trailing down her upturned nose and cheeks, her eyelashes wet as she shut them tightly, focused on the way she was breathing, well he kind of had a good idea that he wasn’t doing too terribly.

“Dipper,” she squirmed against him, restless in his arms. Her voice was a little throaty- and he’d have been lying if he said he wasn’t pleased about that.

“Yes?” Came his coy reply.

“You’re killing me here. Stop teasing. It’s mean,” she pouted and he couldn’t help his smile as he pressed his mouth against hers. Christ, how was she so sexy and cute at the same time?

“I could never be mean to you,” he managed to reply, slipping a finger inside of her, the feeling of her pressed around the lone digit made his cock twitch in his pants, which were becoming increasingly uncomfortable by the second.

One of Mabel’s hands gripped his shoulder as he worked his hand between her legs, adding a second digit as he used the spare hand to haphazardly undo the button on his jeans and yank down his fly, offering some much needed relief to the part of his body Mabel called “little Dipper” much to his chagrin.

His focus on freeing himself from his pants was stalled when Mabel kissed him hard, her lips parting his and sucking on his tongue teasingly. Rolling her hips down against his hand he pushed her against the wall firmly, biting her lower lip as he pulled down his boxers enough that he was exposed to the night’s chill before removing his hand from her warmth and replacing it with the tip of his erection.

There was an appreciative mewl from Mabel, who tried to angle herself against him in a way that would ease the aching feeling in the pit of her stomach but instead he took a firm hand and pinned her to the wall. He let himself set the pace, slow and agonizing as he rubbed his length against that velvety warmth he was dying to sink himself into. With each rocking of his hips he made sure to linger a bit at her entrance. Initially he only circled her entrance, pressed against it diabolically, but then he would sink the head of his cock inside of her until Mabel was making all manners of desperately lewd noises that he was quite possibly addicted to.

These were the sounds only Dipper got to hear. The noises, the gasps and moans she saved just for him. Just like her face there in the cover of night with her damp skin glittering in the light the streetlamp provided. These were the things Dipper kept secret. These feelings for Mabel, the way he loved her more than anything in the world, the way he’d do anything to keep her happy, to keep her safe. The way that no one would ever understand, just because she was his sister.

He couldn’t tease either of them anymore. Despite how good it all felt, in the end, Dipper needed her.

He needed her more than  _anyone_.

Just her.  _Only_  Mabel.

In one swift thrust he sheathed himself inside of her, and Mabel’s hand pressed firmly against his neck, her fingers threading through the hair along his nape, tugging as a guttural groan escaped Dipper. Enveloped by that familiar feeling, he tilted his head back, eyes closing momentarily as he savored the dichotomy between the cold rain all around them and the heat between them.

“Fuck,” he muttered against her parted lips which gasped in response and  gripped her hips over her wet skirt as he pulled her down to meet him thrust for thrust. There was nothing especially gentle or delicate about his movements, the sound of their union making an audible smacking sound that only made him want to push himself harder, deeper inside of her.

He might have faltered if it wasn’t for her moans and throaty words.

“Don’t stop,” she gasped and he obliged her, the need in her mirroring the one in him. He was toeing the line for release and he wanted to take her there too.

“Faster,  _please_. Ah!   _Ah_ , yeah. J- just like that.”

His hand made it’s way between her creamy thighs again and his thumb slid over her clit rapidly, unyieldingly as their hips continued their frantic rhythm. Mabel’s words fell away and all there were left were her noises.

There was only her dreamy high pitched moans in Dipper’s ears as her hips bucked and shifted against him with more desperation until she arched her back against the wall, legs trembling, chest heaving as she came. Her walls tightened all around Dipper and he knew he was done for as he continued to roll his hips against hers for a bit longer before spilling himself inside of her, grunting her name as he pressed his face against her neck.

Unceremoniously he slumped forward and he felt himself twitch between her thighs. Mabel’s hands, now free, combed through his hair affectionately so that it was out of his face before pulling his head back so she could see him properly. She kissed him then, tender and light, like rain rolling down a window pane. First against his birthmark, then on the tip of his nose, and then his lips.

Mabel’s mouth lingered and she smiled against his before pulling away. Dipper felt himself go soft inside of her and he made quick work of pressing a quick kiss to her lips before setting her down on her own two feet again.

The rain had abated slightly, not that it really mattered at this point. The twins adjusted themselves in a hurry, Mabel giggling at the absurdity of having just had really great sex in a random alley while Dipper fixed his pants. When he looked up at her again she had pushed down her (his) wrinkled shirt and and did her best to smooth out her skirt.

“Quit staring, you sexual deviant,” her voice was much louder than it needed to be. Dipper nearly sputtered an apology, but Mabel simply threaded their fingers together, despite her best attempt to sound seriously insulted.

“Why do you always feel compelled to mess with me?” He smirked, squeezing her hand a bit as he followed her back to their apartment. There was something simple in the way it felt right holding her hand as they walked together.

“It is my preferred method when showering affection on my sex-machine BF.”

He blushed from his cheeks all the way to his ears. “You should make that my name on your phone,” he offered as they crossed the street. The light was red but there wasn’t a car in sight and Mabel liked to live dangerously and jay-walked whenever humanly possible.

“Oh, absolutely. I’m gonna make you right-facing-pointing-hand, OK-symbol-hand, hearty-eyes, robot-face, kissy-mark.”

“It’s perfect,” He snorted and raised their laced fingers to his lips, kissing her knuckles as they walked along another empty street.


End file.
